Apologies if being 30 doesn't count but I often get told by my peers (and wife) that I am 30 going on 70. I am probably going to re-iterate some of the above to be honest:
1. Social media/selfies/photos of people's food - Can't get on board with it. I had facebook when I was at uni but barely used it and now can't be arsed with any of it. Selfies because..just why? I can't imagine anything worse than a photo album full of images of me. Also when did people start caring what each other had for dinner? I have a whatsapp group of friends that must be 50% photos of their fucking lunch or dinner. And don't get me started on any article that begins 'xxx caused a twitter storm when...'
2. Being cynical about just about everything - I get irritated by all adverts etc that use cuddly animals/good looking people/something totally random to advertise products that have nothing to do with any of those things. And anyone who gets taken in by those adverts is a c**t.
3. Getting up in the night constantly for a piss, as mentioned above
4. My mates from school who haven't become as grumpy as me who still think jagerbombs are a good idea at lunchtime before the football, and just buy them without asking
5. Working my arse off Sunday through Friday to be healthy (diet, exercise, everything) yet still being a rotund p***k.